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Gate Applications

Okay, last time I explained that the Gate is the second most common dynamic range processors in mixing, and that they are also called noise gates which implies their traditional usage as noise eliminators. Now, this week we’ll be diving into how the gate application removes noise from a recording, removes spill, and reshapes the dynamic envelops.

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Before removing noise from a recording, first you have to know and understand that noise can be introduced onto a recording in many ways. A few examples, Tape media, microphones, microphone preamps, any analog component or an A/D converter. Generally speaking, if high-quality equipment is used, and used correctly, a gate for noise removal might not be needed at any stage of the mix. Noise tends to be more noticeable with sparse arrangements and during the quieter sections of a production in both cases there is less to mask it. One thing worth considering is that noise can become more noticeable as the mix progresses. “Some judgement has to be made as to what noise needs gating and what noise can be tolerated.” -Roey Izhaki mixing audio concepts, practices, and tools.

Another point is that our ears find varying noise levels (breathing) more disturbing than constant noise levels. This fact is taken into account in many noise reduction systems. We have to take this into account when gating a noisy track; varying noise level after gating might be more noticeable than the constant noise level before gating.

In removing spills overdubs are less prone to spill, and mostly we deal with headphone leakage on the various drum tracks. Spill can result in four main problems; impairing separation, which ideally we want each track to represent a single instrument. Combdiltering, this is when any instrument might suffer from loss of focus, impact or timbre coloration if its intended track is mixed with its own spill on another track. Adding dirt, this is whenever an instrument is not playing; headphones spill might add unwanted noise during quiet sections. And finally, interfering with processing which is a loud kick on a snare track might trigger compression and interfere with the snare compression. Brightening a tom track might also emphasize any hi-hats spill it includes. The four spill results list suggests that spill should be removed whenever possible. On occasion, after removing the spill we may find that bypassing the gate actually has a positive effect on the mix. The reasons for this are mostly unpredictable. Regardless, we must remove the spill first in order to learn whether its removal actually improves the mix. It is also worth remembering that processors added later in the mix, like compressors and equalizers, could also have an effect on this.

One of the main challenges with gating is keeping the timbre of the gated instrument. It has already been mentioned that a lower threshold setting would help in doing so. This task is made harder when the wanted signal and the spill are relatively close in levels, especially if they share the same frequency regions. Understand when gating drums, there is often a trade-off between the length of the natural decay and the amount of spill, the longer we retain the natural decay the more spill will escape gating. The spill is often made louder by a compressor following the gate, and the instrument can become louder in the mix for short periods while the gate is open. Decay reconstruction is another solution when the gte shortens much of the decay so no spill remains, and a reverb is employed to imitate the missing decay.

Like compressors, gates are also employed to reshape the dynamic envelope of

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instruments, mainly of percussive ones. You can say a compressor operates on a transient and on what comes shortly after it. A gate operates on both sides of the transient; yet, a gate might also affect the transient itself due to the attack function. A part of adding punch is achieved by shortening the length of percussive instruments. Typically, the natural decay that we try to shorten is below the threshold, which makes gates the best tool for the job. A common practices, is just like with compressors, we must consider the rhythmic feel of the outcome of gating. As gates constrict the length of each hit, the overall result of gating percussive instruments tends to make them tighter in appearance. To soften the natural decay, not shorten it all together, we can use smaller range settings. While on a gate we would dial both fast attack and release for this application, on a compressor we would dial longer, less obstructive settings. One outcome of this is that when gates are employed for this task, the results tend to be more jumpy than those of a compressor. For these reasons, the gate’s range is often kept as small as possible, and look-ahead is employed.

All information in this article was cited and noted from Mixing Audio: concepts, practices, and tools. written by Roey Izhaki